That’s called a jelly jar. They come in different sizes. Look up “Mason Jelly Jar”
https://www.amazon.com/VERONES-Canning-Regular-Wedding-Favors/dp/B07JPYDMKS/
https://www.amazon.com/VERONES-Canning-Regular-Wedding-Favors/dp/B07JPYDMKS/ref=asc_df_B07JPYDMKS/
Maybe this link will work?
Links for when you're ready for that next step
To make your spawn jars Mason Jars 12 OZ, VERONES Canning Jars Jelly Jars With Regular Lids, Ideal for Jam, Honey, Wedding Favors, Shower Favors, Baby Foods, 15 PACK https://www.amazon.com/dp/B07JPYDMKS/ref=cm_sw_r_cp_api_glc_fabc_Uw16Fb9YC5H15?_encoding=UTF8&psc=1
Oat berries for spawn jars (oats are super duper cheap) https://www.tractorsupply.com/tsc/product/producers-pride-oats-50-lb?cm_vc=-10005
Pressure cooker
Hawkings Bigboy Aluminium Pressure Cooker https://www.amazon.com/dp/B000VA26DS/ref=cm_sw_r_cp_api_glc_fabc_pB16FbAE6T3YZ