Eames lounge chair  

I find the chair uncomfortable without the ottoman.
And it'll be hard to find an ottoman later to match the chair.
And it'll be hard to resell the chair without an ottoman.
If I were in your place, I'd wait for a complete chair and ottoman set.

Often the rosewood veneers on vintage 670/671
sets came from the same flitch (sequentially sliced) and were, therefore, matched. You'd be extremely lucky to find a "correct" ottoman unless the chair displays bland grain, which might make it a bit easier.
The missing otto puts the chair at about 60% of what a comparable set would bring, IMO.

Eames lounge chair
Thanks for the messages. It's made me rethink. I guess it also depends on what I'd be able to pick it up for.
Cheers.