Again it is proven that in the internet age, every niche interest has its niche. Also Meccano. There is an extensive and helpful 'Meccanosphere' that is perhaps not explicitly labeled as such, yet just as extensive as the Typosphere. The site of the Christchurch Meccano Club of New Zealand is a vast trove of information, its parts library and galleries are for the metal construction toy much of what The Database is for typewriters.
Any needs for current or vintage parts and spares are addressed by a range of online sellers of parts - some with very complete webshop. The two wheels to complete the 1950-ies Outfit 3 were then easily sourced and these duly arrived for quite reasonable expense by post. Like platens also old Meccano rubber goes hard and brittle; for the rubber parts (motor tyres, drive belts) new reproduction parts can be easily purchased.
Building with the set, the instruction book has a very different approach to what the modern-day Lego builder is used to. Instead of the step-by-step instructions to build a model (or perhaps 3 from one set), one image of the finished model is provided for many different models. For some models a list of parts is given, but otherwise it is left to the ingenuity of the builder to figure it out.
Now with the large wheels also in the set, some of the larger models could be made. These can become more challenging and definitely exceed the attention span of the 7 year old. They are even taxing for the older siblings trained on the Danish construction toy.
Such finished models can be surprisingly large - are quite substantial models, being all metal.
This Meccano is surprisingly enjoyable to tinker with for the mechanically inclined, even (or perhaps especially) in this internet age :-)