I get my syringes from the farm store, usually less than a buck a piece.
Not worth the time to clean them so they go in the trash...
I used veterinary syringes from the local feed store. Let the proseal in them just harden. Later, you can just push/pull the hardened slug of proseal right out. I probably got several uses out of each syringe, but did rotate them out as needed. They are only a couple of dollars each, so buy several.