Look for “Concise” on Amazon. They are a Japanese company that appears to be the last company manufacturing #SlideRules.
You can also check http://sliderulemuseum.com/SRM_Duplicates.shtml to “adopt” an extra #SlideRule from their collection.
Also, it’s pretty easy to find an affordable #SlideRule on EBay.
Welcome to the hobby!
Yup! A circular slide rule is a little unconventional, but has the advantage of never “going off scale”, where your answer is of the end of the rule. For example, when multiplying 4 by 6.
If you want a conventional, linear, #SlideRule, I don’t think anyone is still making them. You’ll have to look at eBay or ISRM. There are plenty of nice, affordable used #SlideRules to be found!