I happen to have a cart very similar to that sitting in my own junk pile and honestly had no clue what a #4 cart was until I saw your pictures here. I don't know what brand mine was but i'll be checking it out next time I'm at the acreage (regardless I think some white & yellow paint will suit it nicely)!
From what I recall the one I have came with wheelbarrow rims/tires but I'm not sure if that was original or a hack-job repair by a PO. The wheel bearings were all shot so they got pitched a while ago and has been sitting in the same shape as yours for a while now.
