I would double check measurements against a pair that fits you in waist right now and compare. Like guy above said, sizing can vary since some brands vanity size and sometimes the way store measure can be slightly different. I have the 107 fit from orslow and it was pretty spot on for me, actually a bit larger than I anticipated
the good news is that orslow does always restock the 105 fit.
I did a quick google search and Frans Boone has a sz 5 in stock right now.
The 105 is the more relaxed fit in Orslow's line up of timeless jeans. These jeans are made in Japan to feel and look like the American jeans of the 50's and 60's and they are made in the best Selvedge denim which is washed and distressed to perfection. All details are there, the standard 5...
www.fransboonestore.com
From their measurements it looks like sz4 is more 34 waist which lines up to your experience in unable to button them.
On topic of IH/Samurai, IH carries a wide range of cuts in different weights. I had jeans, sweatshirt, and flannels from them and have never been disappointed in quality. Samurai I think was much hotter a decade ago. Their 710 cut was very popular and from memory it should be pretty close in fit to orslow 107 or Resolute 710.