There are a few places you can advertise Amazon accounts but you have to note that any new owners of your limited company would have to go through verification.

Calculating the worth of your company would depend on a number of factors such as customer goodwill, inventory levels, turnover and profit. You can advertise your company at a price you feel right and take offers on it from those interested.

Looking at your current store front you only have 1 product which doesn't seem to generate a huge amount of sales. You don't have a huge amount of reviews or feedback which is something a potential buyer would look at. Taking all these factors into account I doubt you will get much interest if you decide to sell.

You may have more luck selling the brand and the IP rights to your product to someone who wants to develop it, I would say you are unlikely to get a huge amount for this.

To do sell companies, brands correctly you probably will need a help of a solicitor.