I don't exactly know why the Maclaren strollers are not in stock many parts. I did not hear about a recall, so I am guessing they are preparing something new, new design launch or something made better, while they are not anymore producing the older design. This is just a guess, though. I personally would still look for older stocks or check pre-owned Maclaren strollers.
Apart from that, I will suggest checking if you cannot get your hands on a TFK Dot 2 which is one handy little buggy, and also will suggest the Quinny Zapp Xpress - it may be you won't find them around crazy much, but it's worth a try. Apart from that, the Silver Cross Pop 2 is a spacious buggy, however it does fold line an umbrella stroller unfortunately. And I will also mention the Inglesina Zippy Light and the Peg-Pérego Booklet as interesting options.