Your rim you are looking for is a Sendel T04 rim, which has been discontinued. Your best bet would be to go to Tredit, https://www.tredittire.com/wheels/
, or Sendel, http://sendelwheel.com/wheels/alumin...er-wheels.html
, and find the wheels you would want to change over to, get four of them for your rig and sell the three good ones of the old wheels, which you can do on this site, at the Items For Sale at the bottom of the site. You can probably get a decent price for the three which will make your upgrade reasonably cheap, and probably just sell them individually.