Now i don't know your location, but you might want to try and widen your search to Hong Nor X1-CRT.
Hong Nor is the real manufacturer of these trucks and ofna is just the brand name used in USA.
I live in Denmark and have owned both a Hong Nor X1X-CR buggy and a X2-CRT truggy and it took my 2 years to break a plastick part. On the buggy however the front tower is in danger when driven by a beginner like me. Not sure that would be an issue on the truck.
This site is where I did most of my hong nor shopping when I had the cars, but I'm not sure how taxes and shipping works if it needs to be mailed to the US.
At leas it will give you a part number for the official Hong Nor conversion kit.
The x2 kit should* work on x1 as well.
I converted my X1 buggy with that kit and it worked nice.
http://www.rcmodels.dk/product-6743-1.php
You can change language and currency at the top of the page, and product combined with shipping lands you at $122, unless you'll be able to track it down somewhere else.