My first thought was a version of the training wheels extenders that are available. These are threaded for 3/8" rear axles, yours is probably 5/16" on your front axle.
There's a version of this available at a hardware store in 5/16". Just the 'coupler' where it's threaded on the inside, so you thread to your wheel axle and then thread in another 5/16" bolt on the outside, cut the head off, and viola' ! Here's one that Lowe's has available, but they are everywhere.
Your build is looking great Uncle Shish! RaT oN~!
There's a version of this available at a hardware store in 5/16". Just the 'coupler' where it's threaded on the inside, so you thread to your wheel axle and then thread in another 5/16" bolt on the outside, cut the head off, and viola' ! Here's one that Lowe's has available, but they are everywhere.
Your build is looking great Uncle Shish! RaT oN~!