How to install drawer slides when the drawer cutout trim is not flush with the cabinet's interior side panels
Your cabinet has what is commonly called a face-frame. There are many, many drawer slides available that will work with face-frame cabinets, either by specific design or by use of optional mounting hardware. A &quot;gap filling&quot; strip is not necessary if you use the proper (sometimes optional) face-frame brackets for your slide.
I think you may be approaching this the wrong way. Instead of looking for special brackets, which would not be &quot;universal&quot; and would only work with a particular drawer slide brand and model, you should be shopping for drawer slides that will work on a face-frame cabinet. Virtually every slide maker has options for face-frame so you would narrow your selection by other necessary (or desired) specifications such as: length needed, full-extension desired?, weight rating needed, soft-close feature desired?, etc.