You can make your normal bath smaller with a bath dam and then use a bath seat. I used the shnuggle bath until my little boy was well over 1 and he never complained but it looks more upright than this one.
We've just stopped using this one (21 weeks) and now are using the Shnuggle one, as above it's more upright so you need to be careful of their heads, but he can splash about more which he really likes!
We’ve got this mamas and papas one and I love it! https://www.babyplanetonline.co.uk/mamas-papas-acqua-bambino-two-stage-bath-pearl-white?gad_source=1&gbraid=0AAAAADFqN34UBRKOOTOqog5e-9gcNm0c4&gclid=Cj0KCQjwv_m-BhC4ARIsAIqNeBt2ofxvkLPKitWQFXSj-xCVnlrrfKCDY1qxrZ3Kqpq0ucXyzxWv6wUaApDkEALw_wcB
I’ve got a bath seat now - they can be used at 6+ months and you just run a shallow bath
In the short term, could you get the big bath warm by pouring kettle water in there? Until the landlord fixes the issue?