Short answer is yes they are available.
Longer answer is that they tend not to be as good- small bits of plastic get chewed up by smaller metal cleats combined with the forces of riding off road. What you can get for SPDs is a wedged cleat, so it’s all made out of metal and gives a slight angle, the only problem is they only make one option currently so it’s not as flexible as the plastic ones.
I’m not a huge fan of the in shoe wedges- in general they are less effective, but they can work well and if you use eggbeaters etc then they might be your best option.
Edit- as above any shop with an I-ride account can get you all this stuff, but obviously you are at your own risk if you are experimenting!