I like the HP/Agilent 65XX series of analog supplies. They're widely available on eBay and surplus electronics dealers for $500 or less. I got a 6555A for this project, $220 with shipping. It's 0-120 vdc @ 0-4a, and 500 watts max. It has both constant current and constant voltage adjustments, and fully isolated output. These weigh around 35 kg and are beautifully built and very reliable. Some versions with GPIB interface may cost a bit more.
just don’t use the HP 65 series for large battery chargers, any back emf ( IE you dial the voltage back or the main quits) and they make a lot of smoke and they are a pain to repair