What's the shop made of? If the walls are metal, yeah that will block radio signals.
An antenna mounted outside the shop should solve the problem. Another option is a directional antenna pointed at the antenna on your house.
https://www.amazon.com/Ubiquiti-NanoStation-loco-M2-Wireless/dp/B00HXT8FFI
(I assume your network is 2.4 GHz since the Amped antenna you listed is for 2.4 GHz. Ubiquiti makes a 5 GHz Nanostation as well.)
The issue with a passive antenna mounted outside the shop is that it will be losing signal strength along the entire length of antenna cable to your extender in the shop. If the extender is mounted next to the window with a short length of cable to the antenna outside, you'll be fine. But more typically (because of where the power plug is located) people mount the antenna outside, then have a 10-20 ft antenna cable going to the WiFi extender. That length of cable can easily cause more signal loss than you gain with the bigger antenna.
The Ubiquiti actually mounts the WiFi receiver in the antenna, so there's no signal loss. The connection is then sent inside via an ethernet cable (where you can use a switch or WAP to distribute it). Since ethernet is digital and spec'ed to work out to 100 meters, there is no loss of signal strength.