Not sure on a good machine shop. It's been several years since I used one and it was for engine work.
Funny I yanked a trailer extension off a trailer I bought a few months ago. Not sure what your mini trailer looks like but it made me wonder if what I have would work.
I appreciate you asking and taking the time to post a pic.

But not what I'm looking at. Bellow is a pic of the base trailer I'm working with from Harbor Freight. The bed area is only 40"x48". Mini.

Going to add a single 2"x2" tube to add 5' 6" in length to the tongue.
I was at the Santa Rosa store Thursday to purchase another portable generator for my daughter, who just got her own place, but the line was too long (> 15 customers), and we were pressed for time, so when I we arrived home later that night... went online... ordered the generator with $40 off coupon... flat rate shipping to your door $6.99. Heck, I spent $23 on gas just going to Santa Rosa and back! crazy!
While in the store I looked at the utility trailers on display. They have a nice selection of trailer parts that could suit your needs.
I'll check out what they have. Thanks.

Trip to SR is costly with gas the way it is.
