British Vauxhall, Borgward Isabella, Volvo P1800

Citroen deux chevaux.

As a joke, a friend put an ad in the paper for an old Citroen deux chevaux that included the following helpful information:
"Never been raced."

Great. Just what I was looking for. So, for example, if her radiator was leaking on a 2008 Hyundai (or 2004 Subaru) that would be pretty hard to get fixed?

How about a '72 Chevy Vega? A car reviewer once wrote:
"Buy a Vega if you enjoy meeting people along the highway".

(We had one. He was right.)

How about a US Volkswagen Beetle? Our classic 1979 was made in Germany, sold in the US, and looks like a Mexican one, except it's a convertible. It's also fuel injected, which makes the parts unavailable in Mexico, sigh.

How about bad spark plugs in any Chevy Votec engine? Can't get those in Mexico, either.

We have made bad vehicle choices!!

Writing a novel set in Mexico. I want to send the heroine to Mexico driving a car (bought in the U.S.) for which it is very difficult or impossible to find parts in Mexico. Is their a make or model of car for which that is true? (Or is it now possible to buy parts for every possible make of car?)
Thanks!

I would simply use literary license if I were you. Suburu is a brand that only relatively recently began operating in Mexico: since 2006. That might be a good make of car for you. We still hardly see them around in rural Mexico.