The reason behind so many places telling you not to use bleach or oxi-clean is simple.
Repeated use of either will break down the fibers of the vinyl laminate used to make the PUL waterproof backing. This essentially shortens the life of your pad and makes the pads wrinkle and crack. It's fine to use bleach every now and then though when a little extra cleanliness is wanted. Just be sure to rinse well and you shouldn't have a problem.
I've recommended several people to a group that repurposes hospital pads. They employ people with disabilities. You can only order 20 pads a month and the shipping is rather high. For me, with shipping, an order of 20 works out to about 80$. They also will provide pads to rescue groups free of charge though which I think is wonderful. (I think they do require them to pay shipping.) ODC merchandising is the name.
I also like ezwhelps laminated pads (the tan ones with the paw prints). They're new, made well, and look nice.
If you're thinking of making your own with PUL and a soaker fabric, it will cost you about 13$ for a 3' square pad.