You could get a Korg - Microkog (mini-keys but a huge fan base), or one from their 'Logue series.

 

I only have a Behringer Pro-1 which I rarely use these days, and I kinda want to sell it because I don't really use it and I need money for a digital organ build project and some guitar gear. But I definitely want to get a Pro-800 or a Deepmind and especially the 303 clone (don't know yet if I should buy the normal or the modded version) when the money is not so tight anymore. I don't really want to buy that much hardware, but at least one or a few analog synths are really nice to have, sometimes I'm really tired with VSTs and with hardware synths I often get different ideas and results than with plugins because of different workflow.

 

I would not get the roland. It's a digital clone that will be replaced with another digital clone as Roland have been doing for 30 years now. Also Roland has in general been terrible at maintaining product support over the years, not that it's important with this product but in general I stear clear of them if possible. Novation on the other hand has been great to update and keep their products supported and the bass station is a nice synth and dirtier then the sh101.

 

Notwithstanding your size and MIDI controller requirements, if I had to pick, I'd go Roland, Roland, Roland.

In case you're wondering, the SH-101 was my first synthesizer. So I'm quite fond of the little bugger. It's a lot more versatile than a single oscillator monophonic bass synth sounds it might be (it's got a sub osc as well, but the filter section does a stellar job).

I've no experience with any Novation synth or keyboard other than the reliability issues I've heard of (audio channels usually, but not only). No such issues with Roland gear - any of the lot - ever in my, or my peers' long experience owning them (Yamaha's got a similar reputation for building tanks - Korg, not so much).

You sound like you're limited by your budget - asking too much of a single keyboard ("it'll need not be any bigger than 1000mm x 36 mm which is the size of my keyboard pullout tray and also 100mm high" is mighty specific), so pick what you can afford, and live with it.

 

I have had issues with multiple Roland synths through the years. Lot of them are plastic with bad buttons. Especially in the 90s. Try and find a JP-8000 with buttons that does not need serious cleaning. Yes the original SH-101 was a cool mono synth and nicely build. But this was many many years ago. Roland has a proud legacy but the things they build and have been building for 25 years is not high quality hardware for the most part.

And yes the original bass station keyboard was also a plastic mess and yes even version 2 is plastiky and not amazing build but at least it's a analogue synth where the Roland Digital clone is just another clone. There has been so many Roland Digital clones over the years so would not waste my money on them. New will most likely come again claiming to once again be better making the last digitale clone obsolete.

 

Choose wisely, SH01A is a wise choice.

This bloke knows his stuff.

https://sunshine-jones.com/wp-content/uploads/2017/11/A-Users-Guide-to-the-Roland-SH-01A-v10Ha.pdf