We first bought the Rcom 90 bird brooder, and then two Rcom 60 last year, which are smaller than the 90 and just as good for neonatal, plus take up less space. https://rcom-incubator.com The 90 is good for older sick cats and kittens and neonatal puppies. Our vet hospitals have several of them. Rcom models are super easy to use and would be the ones I would suggest. You don't need to go for the high end Curadle or one with nebuliser.
There is also the Brinsea brand, but some of those aren't as suitable for kittens so research those before you buy, https://brinsea.co.uk/ NB some vets sites do suggest Brinsea for kittens if you need portability, see https://www.incuvet.co.uk/incubators-for-kittens/ Note that website sells the Rcom under avian incubators . Sorry, I am in Portugal, so those are European sites, but Brinsea is available in US.
Also, look at bird breeding sites and agricultural supplies places rather than Amazon for a better range.
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Bettina Vine
Animal Health Director
The Kitten Connection
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