Another option, depending on your use, might be just get some EVA or PE foam and cut it into a kneeling mat and just toss that down whenever you're fiddling about on the ground.
Or buy a cheap foam kneeling pad from a garden store.
I have a set similar to Poncho's and I got then on Amazon. I find the straps rub my legs a bit raw if I wear them for too long, but they are deep enough that I can undo them without straps and shuffle them along, provided I'm not going too far.They were a life saver when laying flooring!Def