Once you have the specs, try Suspa.com. Nice small friendly company many of us have used already. They can make custom length and force gas springs. If you're lucky the eyelets can be re-used by simply unscrewing the existing ones and screwing onto the new spring. Having the diameter of the shiny rod helps here for thread size. The only compromise I had to make was the width of the eyelets on my new spring were narrower, so I had to add additional spacers to the two existing ones. Mine was around $100 being custom made.