Stripped carburetor drain screw head

[anesde]

First off, thank you to all who asked and especially answered questions about starting a bike after a long rest. I recently purchased a non running '03 GZ250 with about 6300 miles. Excited to get it back running, partly so I can ride it but mainly so I can learn how it all works (strange priorities, I know).

Anyway I got myself a new battery and sparkplug and with a very small amount of starter spray I proved she can start up (for about 5 seconds). Took the carb off, bought some carb dip and getting prepped for a full rebuild.

My issue that I couldn't find using the search function is a stripped drain screw head. Seems that the PO thought it a good idea to grind it down to attempt to use a flathead instead of buying the right tool. I have hit both sides of it (exterior and through the float bowl) with penetrating oil and gingerly tried vicegrips. They started slipping immediately so I stopped. Brought it inside to a side room hoping the warmer temp (it's about 20 degrees in garage) might help me tomorrow after some more oil.

Any input on a better way to remove and/or where I can buy a new one to replace this? Thanks in advance to any help!
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