Where can I watch this?

Sorry for the wildly late reply (How often though am I going to check each and every individual sub-forum of every individual piece of anime media I've ever watched and logged? Especially for the very slow or super dead/inactive ones and ones I'm not obsessed with).

But when I first watched this series back in 2019, these special episodes were included with the main series on the popular pirate websites. Either right alongside all the other episodes and separately marked by a different number, or on a separate webpage which would come up in the search engine alongside the main series as soon as you typed the name of the main series in. As the format largely hasn't changed on such websites, I can't imagine it would be much different in 2023 or now in 2024 than it was in 2019 in that respect. If that's the resource you're using. If you're using some major mainstream official paid streaming service website then I can't help you (I don't think that this now-older somewhat obscure series is on such sites now though anyway).

This may be and probably is redundant given the lapse in time, but answered regardless as it may assist future passersby.