Sure you could use oxycodone as a withdrawal aid. It isn't the best option, but it is do-able if you have good self control. Wait until you are in withdrawal from dope, then slowly titrate your percocet dosage up until you are unsick. NOT high, just out of withdrawals. This is yoursweet spot. Stick with that, and slowly decrease your daily dose by ~20 percent every few days until you're down to basically nothing. Jumping off at 5mg shouldn't be bad, but you could go down to 2.5mg/day if you really wanted to.
Problem is, oxycodone has a short half life so you'l have to be dosing 2-3 times per day to stay out of withdrawal. Don't let the craving of wanting to get high get to you, though, because as soon as you say 'fuck it', and use them to get high one time, you're whole taper will be fucked.
Im' surprised though if you can dope, you can't get suboxone.. Are there any methadone clinics near you? People at the clinics new me stand outside and sell suboxone, xanax, dope, everything..
Just don't give into temptation and stay strong.
Once you find out how many percocet you'll have and what mg they are, we can help you write out a tapering schedule if you like.