Yeah they are still available....the most popular application is in the Marine environment.... Outside that Sears Hardware ALWAYS has them in the nut and bolt section... They have a threaded rod (actually its a bolt immersed inside the rubber plug) there are external threads and a nut n washer ....you tighten the nut and it expands squishes the rubber plug....and it expands uniformly....Work great.....but dont use as the final solution. They are best used as bilge plugs
What you need to do when you come across a stripped out Oil pan is to intstall the next size up "Repair Plug". This type of plug has a tapered tip and special Hardened threads with relief grooves cut into it (to allow shavings to escape) You then install this plug as though you were using a tap and die... It cuts its own oversized threads... 1/4 turn in.... then back out.....so on and so forth till she seats.... This is a permanent repair.... You can only do this oversizing say 2-3 X before you need to move to more drastic measures. The first go around should have you fixed up permanently.
Let me know if you need help finding this item.... I use them all the time
FORGET about your rubber plug......They are for emergency use...and not to be trifled with as a perm solution.