
Hi sabine
you can get packs of transfer paper that allow to print your logo from any decent printer, and transfer to your t-shirt using an iron.
i've used them on cotton t-shirts to great effect, but i think the strechiness of lycra may stretch/crack the logo. I have no idea how they will last with repeated washing.
when i was at uni you could get logos stitched onto t-shirts, but that was 5 yrs ago, so i couldnt vouch for prices.
hope that is of some help