We are not rebuilding Hydro-Vacs right now. Since new vehicles are generally not using Hydro-Vac systems, but are using Hydro-Max or air brakes instead, few new parts are being made to rebuild existing units and old units are getting exhausted. You might be able to finds some rebuilt units around for between $150 to $300. For better performance and dependability we think it is a far better idea to convert it to a more modern system that will be more serviceable in the future as well.
If the system you had came with a master cylinder bore size of 1-1/2" or smaller, you should look at the Hydro-Boost or the smaller Air-Hydraulic system, if it is 1-3/4" or larger, you should look at the Hydro-Max or Air-Hydraulic system for Medium Trucks. With a few measurements we should be able to setup a conversion with more power and features like a backup motor or hydraulic parking brake for your vehicle for a little more money up front, but likely a cost savings in the long run. Call (714) 330-5286 if you have any questions.