I decided to build a quick DIY goal for NBN to play with for now, and in case someone else is interested or wants to build their own I’m posting it here.
The frame is made of 1/2" PVC pipe, heated and bent at most of the joints, and some are screwed/riveted/zip tied together. I used 2 10’ lengths for the sides/back, and then added the 51" and 26" bars on the front. The small bar on the front top is not pipe because I didn’t have any left. I didn’t do the cross braces because the pipe in the current setup is quite sturdy.
The netting might be tricky, so you would have to see if some fabric stores have the mesh like material. I happened to have some plastic like netting from inside an old mattress, which is what I used, and it works quite well but might stretch over time. Because of the way the netting is, it was really easy to attach with just duct tape. I didn’t do the netting and flap for the high goal, so the balls just fall onto the ground inside of the net (behind the low goal, inside the field wall).
The total cost for making this was less than $10, and you can probably do it in less than an hour (I worked on it while going back and forth to other things, so I don’t know how long it actually took).
I used the dimensions from the CAD file, which I also put into the ACAD drawing below. I tried to get them as exact as possible from corner to corner (including the connectors), but it might not be perfect. In case you don’t know what the frame is like, there is also a screenshot of the CAD model.