Obviously you can rebuild it yourself. However, if for one reason or the other you prefer not to, Ross Miller of Speedwell Garage (who posts here frequently) is one trustworthy rebuilder:
Speedwell Garage
206 Dairy RdParktonMD21120
(410) 357-4561
Kanter Auto Products as well (also a source for rebuild kits) and they provide an exchange service, so your car does not need to be off the road. Their rebuild kit also has the option of a new stainless steel plunger.
Kanter Auto Products 1948-54 Packard Parts, Power Brakes is Group 1.322 Max Merritt has rebuild kits and also has treadle vac units available on an exchange basis
Max Merrit Power Brake Units Finally, three more more vendors of note, though I have no experience with them:
Karps Power Brake in Chino, California:
KARPS Power Brake Harmon Classic Brake, has units for exchange and kits.
Harmon Classic Brakes Finally, these guys recently started advertising in the Packard Club newsletter:
Tiger Treadle Vac RepairThis Post was from: https://packardinfo.com/xoops/html/modules/newbb/viewtopic.php?post_id=245304