I purchased a used Roadmaster Falcon 2 tow bar for our Jeep. Got if for $357 on eBay. This worked fine, but I eventually bought the complete service kit for it from Etrailer.
https://www.etrailer.com/Accessories-and-Parts/Roadmaster/RM-910003-60.html The video showing the process is here:
https://www.etrailer.com/tv-review-roadmaster-service-kit-for-falcon-2-towbar-rm910003-65.aspxI also purchased a used Roadmaster EvenBrake 9400 from eBay. Paid $497. Worked well for a year or two, then a seal started leaking, causing the compressor to cycle quickly. The replacement seal was under $10, and took less than an hour to take the unit apart, fix the issue, and clean up the inside. Details here:
http://2manytoyz.com/RoadMaster-EvenBrake-Repair.htmlBoth items work perfectly, but did take some effort on my part. I used to work in the aerospace field as a tech, so this type of work is very easy for me. You can take a look at the links above, and decide if you're willing to potentially do this type of work, or look into having it done. But even buying it new, eventually this type of equipment needs servicing.