The ISP has contracted a service that captures bridges@ and BridgeDB. Meek works but the connection is very slow (60~100 kbps). How do I get obfs4 bridges that they cannot capture?
Bridges that are not listed in BridgeDB are distributed manually.
As such you'd need to know someone or some organisation running such a bridge and contact them to request usage of it and obviously they'd have to actually trust you (i.e. that you weren't trying to find out the bridge address to censor it).
I find it unlikely your ISP has such a contract (there are easier paths to take and I doubt you've tested every bridge in bridgedb), but I'd love to know more if you have more information on that.