MiA merch releases don't feature this gang nearly enough. Here's my effort to catalogue the releases of goods that feature or directly relate to the Sages and Irumyuui (and very occasionally Pakkoyan). Goods are listed approximately in the order of announcement, but I make no promises.
Nov 2022: Popoon goods release (included: brand new art of all three sages and Iru!)
This release featured acrylic keychains, acrylic stands (note: not pictured, they are nearly identical to the keychains), tin badges, note holder clips, and a clear file. I believe this was the earliest-announed (summer 2022) release of goods to include these characters, not counting the manga volumes featuring them.
Dec 2022: Petanko/Penguin Parade goods release (including: brand new chibi art of all three sages!) This release included keychains, acrylic stands, and tin badges; only the tin badges are pictured below. You can view all goods from the release here.
Jan 2023, grand settlement event physical goods: acrylic stands, belaf sleep mask, waz cricket senbei
March 2023 (announce date?) charaum cafe lol waz shorts . goods: coasters, acrylic stands, ?
June 2023, announced April 2023: Usagiza Lepus collab, featuring adorable original artwork of all three sages and Iru! This is also, I think, the only official artwork to feature Irumyuui and Faputa interacting, the former whole and well as a human... ;A; This collab featured a bakery event with delicious foods for sale, all of which were featured in the artwork The artwork (both the main illustration and the individual characters' illustration, as the artist evidently drew each of them completely, including the parts not visible in the illustration) were offered on a huge variety of merchandise.
June 2023: Hoodies by L-label, featuring...well, technically none of the Ganja, but I'm counting it as Belaf merch -- these are hoodies festooned with the tiny narehates that live wtih him. There is a black hoodie (pictured below) and a white sweatshirt version. 
August 2023: Yumtea collab, featuring new art of the three sages posing with bubble tea?!
October 2023 (announced September 2023): Bakudan Yaku collab, featuring new chibi art of the three sages making giant takoyakis!
February 2024 (announced September 2023): color changing mugs featuring Belaf and Wazukyan, adding hot water changes them to their narehate forms!, no new artwork (I don't think? the drawing of Narehate Wazukyan might have new, actually
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