The above article discusses Trump-themed merchandise and its manufacture in Yiwu (义乌), comparing the 2016 and 2020 US elections. I'm struggling with the part in bold:
[My translation:] Slogan bracelets, stickers, small flags, placards (?), broaches, …… Yiwu's big and small wordshops, for the once-every-four-years US election, produces these 饭圈类 products. According to regulations [they are] called president election products.
In the above, I don't understand why 饭圈类 ("cooked-rice-roll kind") is used here (Google Translate gives "rice ring products"). It appears to be used metaphorically.
Question: What does 饭圈类 ("rice-ring kind") indicate in 生产这些饭圈类产品?
(I found the answer while researching this question. I thought it was interesting, so I'll self-answer. I welcome further answers.)