BM Tour

Hi I'm new here with a newbie question, go easy on me. I have inherited a desktop in a Thermaltake case. I want to add a couple of 2.5 inch SSD's and probably another 3.5 HDD. I need to buy additional mounting screws plus 3.5 to 2.5 brackets in order to mount these to the chassis. Trouble is it's been many years since I mucked about with PC's and the mounting screws used in this case are unfamiliar to me (or non-standard or something?). They are black and have what I can only described as a large, turned, shoulder before you get to the head of the screw. Unlike the old screws, it is this turned shoulder that inserts through and supports the weight of the drive against the chassis holes. The ones that I have seen advertised appear to all have the other style (old small screw without shoulder). Could someone point me in the right direction to order these items please. Hoping this is enough info to go on here, but I can add more if needs be. Many Thanks.