You would be able to make DR500 #61410-40400 adjusters work. You will need to machine out/grind/file the round holes to accept the RM spacers. I am possibly going to get these RM adjusters and spacers made in 7075 and hard annodized or in Ti but wouldn't be till later in the year and i guess you want the parts 'now' so probably is no help to you i guess.
Another way you could probably do it is get the PE spacers (2 RH side ones), bush them down to 15mm for RM axle but you will also need to machine out the slots in RM swingarm a little bigger for PE spacers aswell which would mean you couldn't go back to the RM ones then.
