I hear teddy Pardo makes a nice one
There are many LPS (linear power supplies) available in the market that are compatible with the Lumin U1 Mini. Some popular options include the Sbooster BOTW P&P ECO MKII, Paul Hynes Design SR4, and Farad Super3. It's always recommended to do your own research and read reviews before purchasing an LPS.
LHY Audio has a nice lps for the Lumin U1mini. I’m using it on my Lumin U2MINI. I bought mine from Ali Express for $100 cheaper than authorized dealer sells them for. I’m using the LHY LPS 80VA. It sounds a bit better than the Sbooster that I was previously using. Ali has an “upgraded” version and it was only $289 shipped to the USA.