I have seen a few micro rings posted around mainly one by trojanfit.
http://www.trojanfit.co.uk/trojanfit-micro-boxing-ring-1362-p.asp
I think the idea is to train in an area where you aren't able to run and therefore have to focus on blocking. Also it would get you used to being against the ropes, so you don't feel pressured in that situation.
The price range is in the same ballpark as any other big bit of kit for a home gym, and i'de be able to fit it in my garage. (there are a couple of gyms I found that have them, but not close enough for me to justify trying it out)
https://www.youtube.com/watch?v=ZuCEcxU-qo0
Has anyone in the community trained using a micro ring? Did you find that it helped improve your technique?