Question: I work remotely. I'm soon off abroad for a few months and will continue to work remotely while I'm away, taking the company laptop and possibly other similar hardware with me to perform my duties. The trip is my own choice.

My employer has asked if I could insure the hardware through my travel insurance, saying that he doubts the company policy will cover the USA (we're based in the UK).

As the hardware itself does not belong to me and is needed to fulfil my job (without any clauses covering insurance in my contract), is this something I can reasonably be expected to do?

Answer: 
Firstly, check if your travel insurance covers business, or if it's just a tourist coverage. 

Secondly... I'd be a bit suspicious of any company that requires me to insure their own property (you can't buy insurance on an item that you don't have any financial interest in), or any company that can't self-insure something as cheap as a laptop (even a Macbook Pro is pretty cheap in the scheme of things).
Given that you already work remotely and the equipment is not already insured, you should not be required to insure this equipment just because you are going to a separate remote location.

If the company would like their equipment insured, they should do it themselves.