Bottles of a leading brand of Sriracha hot sauce are suddenly hard to find, driving up prices for them as high as $150 — but there are alternatives to opening your wallet that wide.

One of their award-winning sauces, Sambal Kemangi, a green sauce made with basil and fiery green Thai chilis — punches a level of heat comparable to a scorpion or habanero. On a scale of 1 to 10 ...