Tube/Rim lock help

I just ordered the following tires:

Front Tire: Pirelli MT 21 Rallycross (size 90/90-21)
Rear Tire: Dunlop D606 Dual Sport (size 120/90-18)

I'm looking to install a rimlock and Ultra Heavy duty tubes.

I don't know anything about either. Can you please point me in the right direction.

I just got my first rim locks when I bought my current set of MT43.
I intended on playing with low pressures with this set, so locks were a must.
I had similar questions as you.

So, I just bought my shops standard rimlock and had the wheels balanced...without the balance it shook bad. Took a shit load of weight to balance.That made me wonder about double rim locks balancing themselves. Which adds alot of fuss with repairs and maintenance, but adds lock and a sense of efficiency,considering the dead weight to make one work.

Anywho, If you plan on low pressures, do it best you know how. If that aint your thing, and with those tires, frig it all together.

...and with tubes, obviously good quality is a concern, as is correct size, but there are a lot of good standard tubes. Sounds to me like its hard to go wrong with a name brand.
Keeping in mind heavy duty usually means stiffer/tougher. Softer and more pliable includes the tube as well as the tire.
Our bike tends to dictate a stiffer/tube, but a purist or trials style rider would be more fussy than that.

I went with one motion pro lite lock per wheel on mine, they are way lighter than normal rim locks and it takes way less weight to balance the wheels.
I think (cant remeber for sure but its on the package the lite locks come in) the front lite locks are 1 oz and the rears are 1.5 oz, I put that much weight straight acrossed from them to balance the wheels.
Since I dont plan on ever moving the balance weights I put thin stick on weights under the rim strip and ducked taped them into place so they're out of sight and cant fall off the rim, just make sure theres no sharp edges to rub through the tube. I never checked the balance but they dont shake, the stock tires arent balanced so all you need to do is add weight to balance out the weight of the rim lock.

I prefer medium duty or heavy duty tubes, I've been racing offroad for a few years with them and havent had an issue yet.
Save yourself some money and reuse the stock tubes, they're fine.
Ultra heavy duty tubes are quite heavy and arent reccomended for road use they get really hot and can fall apart, they are for offroad racing at low psi, they're harder to pinch flat when run at 6-8 psi other than that they're no better than lighter tubes.

On a side note if you stay above 15 psi you dont need rim locks, I used to air down to 15 psi on my big heavy KLR without rimlocks and never had issues, just be sure to use wd40 or dish soap and water when mounting tires, once dry the tires stick to the rims a bit, dont use anything that will stay greasy and slick.

I installed locks both front and rear - the cheaper heavy ones. After installing the tire I hung it from the ceiling with the axle and a tie down. Then just kept applying stick on weights to the rim until it balanced (heavy part will keep turning the wheel down). No shudder, no shake.....but I'm not sure how long the front rim weights will stay on. I'll probably try the under the rim strip trick next time I have the wheel off.

Biglake hit it with the lite locks! The lightest and easyest to balance.

I put one light weight rim lock on each wheel. The rim locks package states what they weigh. I just put a spoke-mounted weight opposite the each rim lock. Haven't noticed any imbalance even on long paved runs at WFO.

I have MT43's at both ends and air them down to ~8psi for the trails. They still seem pretty stiff compared to a real trials tire. I air them up to maybe 15 or 20 psi for dualsport. Can't remember what kind of tube I used, but since they slowly leak air I'm asssuming they are natrual rubber, HD or XHD. I hate flat tires!