If you have a car that is no longer in production or is very rare, it can be challenging to find parts for it. There are some places you can check and some options, but oval window VW Beetle parts, for instance, are becoming harder to find as the car ages and fewer of them are still around.
When you are working on an older car that is no longer in production, the manufacturer may no longer offer parts for it, so it can be challenging to find any original equipment (OE) parts. It is not uncommon for a restorer to have to resort to reproduction parts and accessories for the car, but the quality of these parts can sometimes be a problem. This means you will need to look the parts over well before buying them.
When you start to search for reproduction parts, it is good to look for reviews from people who are restoring a car similar to yours and who have used the parts. Things like oval window VW Beetle parts made by a reproduction manufacturer likely won't have a huge market, so it should be easy to find some people who have used them.
Often a search online will turn up some reviews of the parts you are considering. Try to find reviews that are more objective. For example, you may find a buyer unboxing a part in a video or a blog post that details the features and quality of the parts. This can help you decide if you want to spend your money on them or if you want to keep looking for other options.
Fit and finish are critical qualities to find in restoration parts, so if they are not high-quality, they may fit but won't be exactly like the original parts.
Many times used parts for older cars are available from other restorers or collectors, but finding something like oval window VW Beetle parts can be tough. If the parts are hard to get, a collector that has them might be willing to sell them to you, though the price may be high depending on the make and model of the part. Online classifieds dedicated to the car you are restoring are excellent places to find these kinds of parts.
Alternatively, an event like a swap meet can turn up the parts you need, and if the seller is not using the parts, you can sometimes get a good deal on them. Sellers at a swap meet are generally there to sell things like car parts. This may be a good option to consider if you are on the lookout for parts that are no longer manufactured.