Bottom-Expanding-Envelope United Kingdom Import and Export Companies

I'm looking for an envelope with a bottom gusset and a paper insert inside - as per the picture below - is this something that you can make? Small envelope - 21.5 x 16.5 cm / lip size - 5 cm Big envelope - 26.5 x 19 cm / lip size - 5 cm 8,000 units a day, per size - 16,000 units a day. I would like to get pricing based on this usage for now. Also, our business model requires Sedex/Smeta audit and BRC certification as minimum accreditation.