I wish that I could endorse the idea of buying the stainless Arkay tanks through B&H, but when I finally broke down and purchased a set of 1-gallon 8x10 tanks, they took almost a month to deliver and the quality is rather poor (functional, but one of them is angled at the bottom to the point that it will barely stand upright).
On September 1st, I broke down and yielded to the temptation of buying an Arkay print washer; after five weeks, it took almost another week to get the fact that the washer hadn't been shipped, built, or even scheduled yet. They did, however, cancel it for me promptly.
Making acrylic tanks is almost certainly the best solution nowadays, since the most common used tanks seem to be ones that will take 4x5 but not 5x7 hangers (don't ask me how I know this...). The only difficulties are likely to be that imperfect seams will create traps for residual chemicals (having dedicated tanks for developer and fix pretty much solves this) and the low thermal conductivity of acrylic means that adjusting temperature quickly by setting the tank into warmer or colder water is problematic. But the same technology that lets you make the tank will also serve to build a water jacket, assuming that you have the luxury of enough time and a supply of tempered water.