The second book in Philip Gooden's Geoffrey Chaucer series is free right now at Kindle US and UK, and the other three books are Kindle UK Countdown deals at £0.99 each for about six more days. Unfortunately the others aren't on sale in the US, but there is an omnibus of all four available for $5.99, which works out to $1.99 each - since the second is free, so you really only need three of them. Or, since these are fairly recent price drops, they may go on sale later in the US.
Chaucer and the Legend of Good Women, #2, free
Kindle US:
https://www.amazon.com/dp/B08DV9ZNJH
Kindle UK:
https://www.amazon.co.uk/dp/B08DV9ZNJH
Chaucer and the House of Fame, #1, £0.99
Kindle UK:
https://www.amazon.co.uk/dp/B08DDD3JDF
Chaucer and the Doctor of Physic, #1, £0.99
Kindle UK:
https://www.amazon.co.uk/dp/B08F7SN8G3
Chaucer and the Vintry Ward Death, #4, £0.99
Kindle UK:
https://www.amazon.co.uk/dp/B08F7VCCFM