I get my lab glass off ebay or aliexpress. I use the Buchner as a primary filter for my ISO, I heat purge , no vacuum and I have never had an issue with residuals. I pulled the boxes of filters out to get the micron reading off them , but it is all in Chinese, lol. I know I bought the finest possible at the time. I use fractional distillation to recapture the solvent, which reduces the overall volume of solvent to later evap/purge and decarbs in the process. I have done the same process with home made 70-80% ethanol (brewed with sugar and turbo yeast, then distilled and checked with an alcohol meter, huge PITA btw. but everclear isn't available in my Province), but as expected it pulls a lot of water solubles. UV treatment clears the green out and doesn't really seem to reduce potency, at least not that I could detect). ISO is cheap , readily available and 99%. With the ISO Its certainly well below human detection levels. If you are purging thoroughly, or better yet with a vacuum chamber, its not a concern. imo
My secondary filter is through a large 500ml syringe with .22 micron syringe filters. The Buckner I use only to filter out the heavy stuff. I am of the opinion that no matter what you put in that porous stone type Buchner its going to clog it up and there is no way to back pressure wash them that I can figure out. The next Buchner I buy will be like the first one you posted. With this outdoor harvest and the popularity of edibles I am going to try some crockpot/cooking oil extractions as the above process is enormously time consuming. I think I will still use the Buchner for filtration, then right into recipes or jarred for later use. Although I have yet to try filtering cooking oil.