An article called Ten Handmade Gifts for the Tabletop Fan in Your Life, published in Tabletop Gaming magazine, inspired me to search Etsy for things a solo gamer might like to order. Besides inserts, trays and card holders, there is a wide variety of custom bits and minis you can purchase to embellish your board games, as well as decorative things for the home, and actual card games.
I am listing here a few that caught my eye, leaving out upgrades to Terraforming Mars because of the recent Kickstarter campaign, mugs and t-shirts with jokes that nobody laughs to, and any merchandise featuring a simple meeple design because that's just lazy design.
1. Custom components to replace cubes or tokens
Wingspan is already famous for looking good on the table, but there is always room for improvement with these Wingspan resource tokens.
If you have Abomination: The Heir of Frankenstein, you may feel that the cubes don't represent blood and muscle tissue realistically enough. If so, you may want to take a look at these Acrylic tokens for Abomination.
And my personal favourite: Deputy token stands for Black Orchestra. The Reich ministers now really look menacing when they get in your way.
2. Game challenge boards
Solo challenges take place quite frequently in the 1PG, and people also set personal goals like playing games in their collection a set number of times. These wooden boards help you keep track of your progress: 10x10 game challenge tracker