Depends if you like what you have?
I had 2 'plastic bottle' type masters my Moke, had them both sleeved stainless steel and cost $160.00 for the pair complete job including new kit (except the lid seal

), but they are original and work fine, will never corrode, and shouldn't fail for years!
My Mini K has a new plastic bottle that looks crap, and seems to build up too much preload pressure, brakes often feel too tight, and you feel like the hand-brake may be on a bit...
But I agree, local brake shops just send them out, and then build them when they return from the machine shop, maybe you can find the machine shop, cause they are simple to build up, may save you paying some one else to do a simple job!
Cheerio,
Chris