For another next build, or if you pick up a briefcase which don't fit your rails so good. I found those today for quite a reasonable price. 

https://www.etsy.com/ch/listing/266275709/hulle-bugelsets?click_key=3dd7af737fb83120682b77c1d57100abee8d2932%3A266275709&click_sum=c7ce6fec&ref=sim_strv-3&variation0=2190176709

I maybe gonna get some for a reboot of my  modular modular case.