Then inspiration struck me. It was a rust monster...

The rust monster is another iconic creature from D&D that originated from toy monsters that were made in Hong Kong. Based on general appearance, it's likely that the toy was modeled after Kemular (ケムラー), also known as the Poison Gas Monster (毒ガス怪獣; Dokugasu Kaiju). Kemular does not have antennae, but the tail and back (with the wing case folded) seem fairly analogous to the rust monster. In any case, rust monsters are the nightmare of any character with magic weapons and armor made of metal.

In old school illustrations, rust monsters were not particularly big, but in later editions they were portrayed as much larger creatures.

I like the original way in which they were presented as whimsical creatures, like in The Very Hungry Rust Monster by Steve Dismukes. I don't think every monster needs to be huge and menacing.

The miniatures of rust monsters in my collection include the Archive Rust Eater from the Dungeon Nasties II blister pack (Fantasy 5040), the Grenadier Ruster Beast (Monster Manuscript Vol.IX 1509, MM74), and the TSR Rust Monster (AD&D 5612).

The Rust Eater has the bumpy skin of a rust monster, but is bipedal, with aardvarkish features. The other two miniatures are pretty consistent in appearance to the original plastic toy.

As far as size goes, they're all probably about twice as large as I would prefer them to be, but they do not look overly large if you consider them to be later edition rust monsters.