Never have this problem because some of my doubles buddies have good serves.
I guess the best way to practice return of serve is to look for people who serves well, and play them.
And in a nearby university tennis center here they have a ball machine which can feed pretty powerful balls. If we could elevate it like what Agassi's father did......
Head Pro Tour 280 349g 7.6 pts HL / Razor Code 18 & Powergy 16 @55 lbs