Ok, I ended up calling a couple of places this morning. No one has ever seen a 3A version of these (even though it is made). It seems two of the suppliers for the Navy DC panels are the only ones that actually use the on a regular basis. 2.5A or 5A was all I could get and needed to choose for my Lowrance LSS-1.
The LSS-1 specs a 3A fuse. Current draw is listed at Max: 0.75A, Typical: 0.60A, Inrush: 4.7A peak.
I chose the 2.5A (medium delay) with the thinking that if the inrush of 4.7A doesn't pop a 3A blade fuse, then it shouldn't trip this breaker. And, 2.5A is well above the "Max" and "Typical" draw requirements. Is my thinking sound????
Also, found that Airpax makes these too and the Navy doesn't mind this brand either:
See "SEALED TOGGLE CIRCUIT PROTECTORS (IAGN/IUGN)" on page 5.