How about SEIV T-shirts and baseball caps?
And SEIV bumper stickers and windshield decals.
And action figures of each of the races.
And a SEIV collectable card game
SEIV towels
SEIV cereal with little bits shaped like spaceships.
SEIV watches
"I imposed my dictatorial will upon the entire galaxy and all I got was this lousy T-shirt."
If you want SEIV merch... print your own. Many modern printers can print onto special paper which can then be ironed on to T-shirts. I have some Viking designs I really ought to get round to printing...