Since the SSDs we have are 2.5", we need a special adapter disk tray, which Dell refuses to sell us.

Our first option is to buy second-hand disk trays.

There is also now a dedicated company manufacturing and selling Dell-compatible disk trays: https://www.workdone.biz/
They are selling them on Amazon and we need this exact model: https://www.amazon.com/Hard-Drive-Caddy-PowerEdge-Servers/dp/B074L3FB79/ref=sr_1_3?ie=UTF8&qid=1527075002&sr=8-3&keywords=dellblade .