Hello and Welcome to the board :D:D:D
Maybe contact your local quilt/fabric shops, put up flyers there with what you need. Put on the flyers the dimensions for the isolette covers. Print out patterns for the positioning aides and leaving copies there, or put website addresses on the flyers.
Contact your local quilt guilds too! Most have charity projects, and their members may do some on their own as well.
Also, you can post the need here in the Main section of the board. Please contact our moderator, Patrice J by PM first, to find out if you need to reach "regular" status before you are allowed to ask for donations.
Is there a way that these donations can be mailed to you at the hospital's address?