By SLP, what type of bed do you have? Does it have wooden slats at the bottom etc? We use Japanese silk rope for arms during most of our sessions and use a spreader bar attached to a rope at the bottom of the bed for leg restraints.
Probably best for you to look at something similar to this
Rather than getting one under bed restraint, we found that getting the ones which have four separate ties and cuffs work better for most beds, unless you have a divan! Haha. We even bought some cheap picture hooks once and screwed them into the bed to give us the ability to tie anything to them.