Adjust Temp on HJ-40 cartridge?

My shower never gets hot enough and I would like to allow for more hot water to come through. I disassembled the handle and the cartridge is an HJ-40, seen here: http://www.vimadecor.com/retail_product_detail.php?id=1451&cid=46&subid=0

I cannot figure out how to adjust the hot water limit on this thing...if it's even possible. Does anyone know how?

Thanks.

There should be a "limiting" ring that fits over the cartridge to control how far the stem can rotate towards the hot side. The cartridge itself is NOT adjustable.

Thank you. I now have it adjusted, but I lost one of the gasket rings in the wall and now it leaks. It is the seal on the very back side of the cartridge and is shaped like a bubble "T". Do you know if I can buy just this ring or do I need to replace the whole cartridge? If I can buy the ring, where?

I have never seen those rings sold separately. There are literally dozens in not hundreds of different configurations. Who would want to stock those???