I purchased this Matris kit (F15H265K) from this ebay add: https://www.ebay.com/itm/276185777895
The seller was Racing_one_Lab and this is their ebay market: https://www.ebay.com/sch/i.html?_ssn=racingone-lab&store_name=racingonelab&_oac=1
No affiliation with the seller but I had a great experience and highly recommend them. When you order there will be a notes section on checkout, in there you need to put in your weight, how you use the bike, and whether you generally ride solo or with a passenger so Matris can send you a set with springs calibrated for you.