this is a cool thread!
Osmium, I'm no chemist, but I think any radical initiator worth its salt should make the reaction "fast enough". Otherwise, why would chemists use it for that purpose?
Rhodium, I doubt water's a problem. That paper says they use "21.35 M HNO3", which weighs 1.345 kg/L, placing its concentration between 50 and 60% w/w according to my merck index. (wierd)
I plan to research the use of the Fenton reagent as radical initiator some more. It would certainly bee the most accesible thing the average bee could get, though benzoyl peroxide can be found by those with excessive acne...
You could basically throw in a little bit of iron powder and H2O2. The nitric acid would make the salt for you, and away you go.
Awesome topic. Combined with an OTC method of reducing nitrostyrenes, I think we could have a real winner in the mescaline dept. here.