So you're looking really for a light highly breathable shell smock, and a thin insulating smock. I assume you will layer over with Down or Primaloft when stationary? How did you select these? Borrowing from someone you met?
Option 1 - Get your Rab. What is the issue with getting your preferred Rab items from the UK? There are dealers which ship international, turn Google to look only at UK and go through all the dealers and find one which ships international, then compare price. I buy from UK about twice a year for 4 years now and never a problem, takes 1-2 weeks to deliver. The challenge is fit & style if you've not tried on before, so I usually pass through the UK try for fit then months later in a sale buy online and patiently wait. I'm usually thinking 6-12 months ahead.
Option 2 - Montane seems to a limited set of suppliers in USA but they don't carry the full range. As has been mentioned the nearest equivalent in Montane for the shell smock is Spetr but I find it just a weird idea. The equivalent thin wicking close-fitting fleece would be the Fury
Option 3 - Marmot. The equivalent breathability of event in a more commonly available USA make is Marmot's Membrain. I've owned eVent (Rab Drillium) and Membrain and they're very similar breathability. In Marmot the nearest equivalent, I don't see any options in smocks so jackets is the Mica (the least durable), Aegis (more durable). I own both. The Aegis in SMALL fits me, and I'm a medium or sometimes a large in other makes, the Aegis short-cut which I assume you prefer?
When you say "Alpine" are you wanting RAIN protection? Many doing Alpine just want shower-proof water-resistance for any melting snow and combine a windproof with a some pile, like the Montane Krypton (I bought yesterday for $60) or the Rab VR.
Option 4 - Paramo. I used to use shells and fleeces but I moved away from them as a shell can be damaged and lose its waterproofness and any type of modest/high excertion swamps a shell's breathability. I moved to Paramo for winter / cool conditions as it combines insulation with waterproof and high breathabilty, much more breathability than eVent. When its too warm for Paramo its too warm to care about being wet in general.
For Alpine use, some use Paramo such as the Velez Adventure Light (VAL) smock which is short-cut. I have a good experience buying Paramo from within USA from Foothills. I use the Paramo Quito but if you want a smock then the VAL.
http://www.foothillshiking.co.uk/ what you do is buy off their website then email them explaining you're in USA, they'll remove local salestax (20% saving!) and then add postage, usually about $12 to USA.
Option 5 - REI. If you want to absolutely drive down the cost, consider REI's own brand you can get an eVent jacket quite a bit less, but again, patience for their sales. I just checked REI now and none on sale.
Probably from all of the above, the cheapest+fastest is look at Marmot. I personally think if its cool enough, then Paramo is the best quality.