I've not used either of those pumps, but the IMED is a medical pump and it probably would be happy with tygon or similar tubing that is about 1/8th inch OD. Depending on the ID, you would get different flow rates. Online I see where it can pump at 0.1-999 ml/hr, which is 0.002-16.65 ml/min. On diameter of tubing may not cover that entire range, you'll have to test the tubing you get and see.
Isn't the Hamilton Microlab 900 a syringe pump? If so, then it's not a peristaltic pump and you can probably vary syringes on it to vary the pump rate. Keep in mind it will not have a constant flow like a peristaltic pump if it only has a single syringe.
I've got some tubing you can try if you want me to send some. Send me your address and I'll send something off this week.