eBay store 'Everything Alfa' with seller misterfiat out of Atlanta appears to sell new ones for $11. Google brings up sold listings, but as of this writing his eBay store lists them as available. Number of parts sold and estimated shipping dates suggests he might be a reseller rather than a distributor, but all that matters is he's got a source and a decent reputation as a seller.

Here's a current link to the 38mm x 600mm corrugated paper hose
https://www.ebay.com/itm/204401814450?hash=item2f974c2bb2:g:DdYAAOSw00pkt-RC

Here's a link to their store catalog with lots of P1800 odds and sods stuff
https://www.ebay.com/sch/i.html?_ssn=misterfiat&store_name=everythingalfa&store_cat=37618414014

Here's a direct link to the Mr Fiat website https://mrfiat.com/ with contact information including phone number. Same prices as his eBay store. Reviews on other car sites suggest he's very responsive, even allows pickup in North Atlanta.

Also lots of interesting 240 stuff in his catalog for others following this thread. Prices aren't cheap compared to other aftermarket sources, but some stuff you simply can't find elsewhere. Skandix in Sweden is also a good source for rare parts, expecially OE, but shipping and duty makes them a bit prohibitive for North American buyers.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now