If you want a proxy that no one can use then you have to pay for it (i think) such as vpn hotspot shield, this is what i use when i'm on my main account, if you're going to autobuy on your main account then please don't, i recommend using a shell old enough to restock whatever you want and use a proxy to access the account and a proxy when on the programs you decide to use on it, no point in auto buying on your main account as it will put your account in danger even if you are really safe, you might make one mistake and boom bye bye main.
So i recommend to use VPN hotspot shield on your main and to not auto buy on your main, just auto buy on a shell account and once the items you restock have been secured for a month or two (or however long you want as it is ultimately is your decision) then transfer them to your main, you can either gift them to your main but i don't recommend transferring more than 2 items as it might be flagged as buying items. If you restock a lot of items then put them in a trade and transfer them that way.
I hope i have helped you in some way, if you'd like anymore help then feel free to PM me and i will be more than welcome, if i can't help you with a problem i will try to direct you to someone who can