There's clearcoats available in both semigloss and flat - yer mebbe jus' gonna hafta order it from somewhere as I've not seen it available "off the shelf" except in small quantities at a hobby supply store... ofc that might be all ya need anyway lol
examples only, shop around for better brand/prices;
12 OZ, Crystal Clear Coat, Flat Finish Spray Enamel
Eastwood Diamond Semi Gloss Satin Clear
edit: I'd reco goin' with the semigloss BTW - it's a **** of a LOT easier to keep clean & nice lookin'