I'm completely out of my element and traveling home tomorrow. I can't get anything... I was thinking to try and score heroin so I don't get sick but its been years since I've done that.
I'm not going to lie, if it was a choice between being around my family while I'm kicking a 300mg oxycodone habit sick as a fucking dog with only OTC meds or scoring some heroin so that I could enjoy my time at home and prepare the detox for the near future in ideal conditions, I would definitely choose the latter.
As I'm sure you know, scoring heroin on the street isn't difficult at all. Do you have a script for your oxy or a dealer? If its a script then there's a slim, slim possibility that if you call your doctor and tell him that you've had a house fire or gotten robbed or some other excuse, he might reissue your script if you're lucky. If it's a dealer you get it from and the problem is that he's out of oxy then if you ask him he might be able to help you out with heroin instead. Or hopefully you'll know at least one junkie and then all you'd have to do is offer them $10 for being the middle man and I'm sure you'll get some heroin really quickly.
Failing that I've heard in America (I live in the UK so I have no personal experience of this) there are designated ghettos where it's really, really easy to score drugs. Again, I'd much rather do that then cold turkey with a habit your size. If you have a gun or a buddy or two you could take for back up it might be a good idea just in case, and I'd only go with an amount of money that you're okay with losing at first just in case you get robbed or ripped off.
Other than that, one method that has never before let me down when I've been in a new city with no connects and started really craving some heroin is to just go where there are plenty of homeless people and start asking them. As long as you follow basic common sense rules like not to front them the money and only getting a small amount at first till you establish some trust with someone then you should be fine.
To be honest I'm surprised you haven't already gone from oxy to heroin when it gets to the stage you're taking 300mg of oxy per day. In my opinion the only significant difference between heroin and oxy is the added stigma attached to heroin. Perhaps heroin might be a little more addictive and a little more dangerous as it's more sedating, but honestly IMO there's an enormous potential for addiction and risk of overdose there with both and the differences are not anywhere near as significant as the difference in stigma makes out.
So since you're already taking 300mg of oxy a day, what's stopped you from switching to heroin? Is it just the lack of availability? Practically all the addicts I know by the time their pharmaceutical habit gets that large it's inevitable that they will soon be taking heroin as trying to maintain that kind of habit with pharmaceutical opioids is just not financially sustainable unless you're really fucking loaded. Especially when it gets to the point that they're spending ridiculous sums of money per day just to maintain and not even get high, heroin starts to look a lot more tempting. So what is it that's kept you on oxy?