I noticed recently that my GPD Win's bottom shell was swollen. I assumed that I could order a replacement battery pretty easily and was surprised to learn that they are difficult to get and pretty pricey. I didn't want to spend $50 for a replacement only to have the same problem next year. I started to search for alternatives. I fly rc helicopters and multirotors so I didn't think it would be difficult to find. I was mistaken.I think I found a good replacement for low cost and wanted to share with this community as I've found a ton of useful information on this board.I've had great success using an LG battery in a Raspberry Pi portable that I made:So when I came across a post online suggesting that an LG G5 battery was about the same length and width but half the height I searched for specs and decided it would be worth trying to use two of them in parallel. I was able to order 2 2800mah G5 batteries from ebay for under $20 shipped. These would be great as they should be easy to acquire for some time. Once I received the batteries I compared to my GPD Win stock battery and found that 2 of the G5 batteries stacked were very similar in size. I connected them in parallel and have used my GPD Win through one charge/discharge cycle so far and they are working very well.Here is how I prepped them for use:Hope this helps some of you looking for replacement batteries. It would be great if there were a very thin compartment with spring loaded contacts that 2 batteries could fit into in a parallel configuration with the GPD Win connector on the compartment. That way batteries could be replaced without soldering.