Actually, your existing drums in manual mode should be even easier on the foot than disks. That is because drum shoes have a "self-jamming" effect, which is why they are touchier if gummy stuff gets on the shoes. Almost all cars since 1980's have a booster because of the front disks (73+ federal mandate).
Cheapest would be to buy a manual MC, which usually comes with the rod and should be a direct bolt-up and free up space and weight in your engine bay. Look for a 1"D bore max.
Another approach would be adding on an electric vacuum pump. Many cheap rodders have taken to getting the pump from a junkyard VW diesel of the last 10 years, maybe $50. You can find on ebay. I have been thinking of getting one for my M-B diesels since the engine-drive vac pumps are expensive and problematic.