Here is a local company here in the states that supply parts for small engine driven rides. Go Kart Parts | Go Kart Supply Online Catalog
I recommend taking the time to build a sturdy ride over just slamming together some pieces from here and there.
In my youth years I was really into build go-karts and racing at the local tracks in Florida. My father pushed the issue of using the correct tool for the job, and the same principle in using the correct parts for the project you envision as well.
So, over the years of scrounging and scabbing together stuff, I always made the extra effort in finding parts suitable for my projects too. So to not step on anyones' toes or dent someones' bubble, I am offering places to gather those parts for our builds.
After being in the rat-rod, and custom low rider street builds, I have always preached safety over anything else, especially on all the forums I have visited.
So this place is no different to me, I will offer my engineering skills and places to get it done right the first time round. Just good general building practices to share with everyone. Be safe and we can live to share our stories with all.