1/144 Models & TAG scale

Gundams, even the 1:144 scale ones, are significantly bigger than TAGs.

 

I know it's an older TAG, but this is the best I can do on short notice. The big fella on the right is a 1/144th high grade (Turn A Gundam), the smaller ones are Assault Kingdom figures (A Kampfer and a Zaku II) which I included as they are a closer fit.

 

The issue is that you're aiming to add to the Guijia, which is not a "proper size" TAG, but a mini one. Full sized TAGs can get away with some weapon or part switches (and can benefit from the fact that they sell standalone weapon packs, you can get just the guns), but the Guijia is just too small for this.
I do believe even the Guijia can benefit from stuff from that part of the modeling world, but you'd have to look. I'll see if i can ask some buddies that are heavily into gunpla and see if they have some ideas.

 

That Zaku is smaller than a "proper" 1/144 kit, however.

 

https://www.ebay.com/p/KOTOBUKIYA-M...ds-MW40-Weapon-Unit-Multi-Caliber/24012062203

Try small guns and use plasticard cut them down... it's a one off so go plastic/model kit mix... if you look you'll find one

 

Something smaller than an old Guijia's gun?

Have you looked at Maxmini, Kromlech, or Anvil Industries for their 40k bits? Just be advised that it will be a pain in the butt to cut off the big gun.

 

I removed the big gun from old fatboy guijia and it really wasn't much more than "clippers to the fore" and "yoinks, away" - but I had no interest in PRESERVING that which I was removing. If you want to KEEP that bit, then yes, removal can be a PITA.

That said, I removed the new version's gun from its back mounting hoop and made it hand-held (so I had to carve a new back-hoop to replace the bit that is PART OF THE GUN. Unless you know what you are looking for, you'd probably miss it (it's not a perfect replacement, but it's close enough to pass casual inspection).

 

In that case, try Anvil Industries 'Negotiator' anti-materiel rifle.



Size comparison image from Anvil: