Singer Bags ??
While many older Singer vacs did use Eureka H,L & even K this is the one with the top mount hose with the fill tube turning to the back.I don't think there was a same Eureka bag for this Singer.Should be an easy way to find a bag(maybe even micro filter)that fits.If you can find a local vac or hardware store with several type bags it is always good to have the vac with you to try different sizes.
Good luck.With care an less use at a vacation home this Singer might have years ahead of it.(If you end up with weak suction you may find you have a good vac with a bad hose.Do not discard as you might reuse hose ends if this is the case.)