There's actually a website that talks about it. So a few weeks is an optimistic estimate for 11 characters. You may want to constrain it to a lower character count accordingly. I don't know what his benchmark 1.5G processor is compared to a modern PC.

https://opensource.com/article/19/8/how-create-vanity-tor-onion-address

Here's a more recent tool
https://github.com/cathugger/mkp224o

Here's a NVIDIA GPU miner:
https://github.com/dr-bonez/tor-v3-vanity