Philco Freezer - replace/repair seal & plastic around top

Well, you can find a universal gasket kit. Instead of being one solid piece specifically made for you model, It is made up of pieces that you cut to fit. I should warn you that these kits are very difficult to work with. If you dont create an air tight seal, the constant warm air leak will make it run longer, decreasing its useful life.
You said however that the gasket is only dried and rock hard, not that it was torn or falling away from the door. If that is indeed the case, and you still have good tight seal on all four sides, you might be ok for a while.
factory replacements are nearly impossible without a model number for reference.

Good day,
Unlikely you would be able to repair if the inner liner is coming apart.
A local appliance parts house may be able to supply universal gasket to fit to the machine but again, if the inner liner is bad it could prove to be fruitless.

Oddly enough, if you visit supermarkets you will see chest type freezers with no top at all.
Seems like a terrible loss, but it's not.
Cold air falls, hot air rises. When the freezer generates cold air it doesn't spill out the top. It settles into the bottom of the freezer, and stays there. Likewise, warm air rises and has no interest in going into the freezer cavity.
Bottom line. Very little loss.
If appearance doesn't matter, and you can get it close, you should be able to continue to use it.
Your choice, but I thought you would like to know the physics involved here and how it does or doesn't affect you.