it looks like ledil.com has one reflector and one optic that fits in your 20 degree requirement. check them out, if you see one you like you will then have to search arrow's or mouser's websites and see if either one have it in stock.
I second the hyper boost. Not sure if I would use an optic with the MKR. The four dies in each emitter might leave you with dark spots. I have an MKR in a 73mm smooth reflector and it has a dark spot. I have a second in the works using a 52mm Orange Peel reflector, no donuts with the OP.
i used ledengin 4 die leds with their optc 35mm tir, they make them as narrow as 15* no dark spots, google led engin, their lz4 leds are very similar to mk-r led