Getting lenses for Ronja

Worldwide

Atommann from the #twibright IRC channel sells the 130 mm glass lenses by Hong Kong post. 2017-05-08 1 lens 45 RMB = 6.51 USD, example postage 4 lenses to Germany $27.7, to New York $27.7. His e-mail is atommann@gmail.com . He lives in Shenzhen, China, where all the world electronics production is concentrated. He used opensource gEDA and built a picture phone (another image)

United Kingdom

Pound shops like this one in North London. In this one you could buy 100mm lenses.

Czech Republic

Prazska trznice Bubenske nabrezi 13/306, Praha. Usually have in the stall next to the main entrance, but they use to have it also at other stalls. The last reported price is 75 CZK/pc (from 2004). Lens w/rim 130mm, w/o rim approx. 128mm, rim height 22mm, lens thickness in the middle 18mm, lens weight 320g. The dimensions tend to vary.
steebe (at) seznam (dot) cz Kolin, CZ. Loupes from the Vietnamese, 100mm for 15 CZK, possible to send even with the handle, they are clear and they are many. Somewhat longer focus.
Hulin / Chropyne on the market in Chropyne it was possible to buy 130mm loupes for 120 CZK (possible to negotiate down to 100 CZK).
Dioptra loupe with 130mm glass lens. 2017-05-07 in stock, 472 CZK.
The dimensions of the 13cm lens seem to be: lens w/rim diameter 130mm, lens w/o rim diameter 128mm, rim height 22mm (plus protrusion for holder attachment), lens thickness in the middle: 18mm, complete weight 365g, lens weight 320g.

Slovakia

Bratislava, Trznice na Trnavskem myte, but very expensive and max. 100mm. Or in shops "vsetko za 30 Sk a viac", where you can usually get 90mm for 60 SKK.