Scan your local craigslist. I like the Weaver brand. My 2 ton Weaver is as stout as you will find. It may be old but they really don't make em like this anymore. There are some great new jacks built but are BIG $s. Weavers appear on CL for $150 and under, are totally rebuildable, easy to disassemble, parts readily avail, AND lifts to 25"......almost all you see lifts to 19-20".
Look at
www.garagejournal.com and search for Weaver. Great website and lots of great info from alot of tool nuts over there. Poster that goes by Hyball is the resident jack guru and can help you with all your parts needs.
Also.....US Jack frequently has their 6 ton stands on sale for under $90/pair. Some folks freak out at that price but IMHO you can't put a price on safety. Plus they are super nice. Puts my old 5 ton Hein Werners to shame.
Whatever you do ALWAYS lift with the jack and support with stands. A local got killed this summer as he was lifting and supporting with a jack only. It failed and crushed him. Terrible to even think about. We have all been there at one time or another....I will only be a minute, don't want to drag out the stands, etc. I feel bad for his family but we can all learn from this.