I put "Feumaidh mi fuaradair fuar". This should be accepted. I learnt fuaradair for refrigerator before starting this course and it is listed in LearnGaelic's dictionary, so it is clearly not only an acceptable word but less 'English' than 'frids'.
I'm glad to see that. I've had a discussion with a native speaker who said they know feumaidh mi X is perfectly good grammar, but that they use/prefer Tha feum agam air X. I shall also try this style elsewhere when opportunities arise.