I think the gadget shop items are available based on what raw goods factories you have. Have you built all 4 of Wood, Cement, Brick, and Steel factories?
I that's not it, the only other thing I can think is that maybe you need one of the other utility buildings. I can't be sure I'm afraid, it just appeared for me without a problem.

Not only this, but you also have to upgrade the goods factories (enter the factory and you should see an option for it).

That's right - nice catch. Thanks for having my back.

thank you all i figured it out, a feel so daft lol. I always remembered playin the game on playstation and i would rush into upgrading the factorys and spend too much money, so then i though i wont bother uupgrading. I've seen the error of my way lol thanks

This is an old thread but thinks this is the best place for me to answer this
If I were you, I'd go with a Halotron extinguisher. If you haven't heard of it it's the Halon replacement that doesn't bond to your lungs so it won't kill you to be exposed, but has all the same benefits i.e. doesn't harm things and doesn't leave a residue. www.toughout.co.nz is also one of the best store which provide their user some beautiful sheds supplies and different others items in Auckland...

A 5lb extinguisher is about $120 and an 11lb is about $350, but worth it IMO. I really need to order one for myself--I want them for my outdoor kitchen to fight BBQ fires. They're the only thing that won't harm a smoker or require a massive cleanup job.