Welcome from Perth Western Australia.
I've just downloaded from Cousins for you the parts list for the 6119c movement and attached it to my post.
Yes it would seem the mainspring is still available from cousins UK.
It is a 1.05 x .115 x 420 x 10.5 Automatic
( GR2534X )
Other parts are limited though.
Welcome to the forum.
Good day everyone my first time at a watch forum I have a Seiko 6119c 6023 in real disrepair I would like to have a parts list for it and if you can still buy the main Spring nos not even sure this is where I as a newby I should be posting But Thanks in advance regards bob
Well, thanks for the numerous suggestions and ideas everyone. It’s one of those things where you don’t know how it will go until you start. At the moment the movement is giving me a hard time. It was running fine before I touched it. Having cleaned, oiled and reassembled it, it is decidedly sluggish. Runs ok’ish dial down but, dial up it stops altogether. Just out of curiosity, I did do the right thing in oiling the pivots? It’s a non jewelled movement. I oiled the train wheel pivots and balance.