It seems like overkill to transmit QRPp WSPR on a rig capable of 100W so recently I purchased a WSPR Transmitter from Zachtek.
I went for the luxury option and got the Desktop model which is nicely boxed up and comes with a GPS antenna on a long cable.
The GPS antenna is sitting up at a window with a pretty poor view of the sky but it does get a lock as shown here in the Windows control software.
Today, I'm transmitting 200mW on 40m and doing fairly well on an end-fed antenna. These images are from the macOS version of WSPR Watch which is now native for Apple Silicon.
200mW into about 20m of coax and then an end fed - it's doing fairly well. I'm very happy with the ZachTek transmitter and recommend it.