Some older local bike shops have a bucket or box of vintage components in a back room somewhere. You might get lucky and find some used friction shifters from decades ago that fit onto the downtube bosses for a couple bucks.

If so, you could try them out while you still left your bar end hardware installed to see if you prefer it or not. If you like them but decide you want indexing, I do not know if they made 9 speed indexed bar end shifters or not. I have some older 8 speed indexed downtube shifters that I bought used with the hardware to install on bar ends - I think someone used them that way on a triathalon bike.

Quite frankly, I used downtube shifters in the 1970s and hated them. I bought a set of bar end shifters in the 1980s and have used bar end shifters ever since.