Not enough information to do anything with. You don’'t say if you want the bare sensor, or one of the modules (and if so which exact module.) A google search of the form “fritzing part MQ-137” turns up a variety of hits on MQ type sensors (not the 137 directly though) one of which may do.
Peter
You need to provide a web site that describes exactly the module you want as a google search of the form "MQ-137 " indicates there are several of them. There is a template in the parts help category which specifies the information required to request a part. Basically that is a web site with the physical dimensions and connection information for the exact module you want.
Peter