I don't know anything about Pure Land, but I enjoy googling things. Here's what I came up with, for what it's worth:
From the start of Kumarajiva's Chinese Lotus Sutra:
At that time Śakra, king of the devas, was also there, attended by twenty thousand devaputras. Candra, Samantagandha, and Ratnaprabha, and the great devas of the four quarters were there, together with a retinue of ten thousand devaputras.
The translation isn't clear: Candra, Samantagandha, and Ratnaprabha are themselves Devaputras, sons of Devas. This may or may not mean the same as Deva, let's suppose it does. Their names mean 'Moon', 'Pervading Fragrance' and 'Treasure Light'.
There is a somewhat dodgy Chinese tradition identifying
the deva Candra/Moon with the name Treasure-happiness and the Bodhisattva Mahāsthāmaprāpta
the deva Samantagandha/'Pervading Fragrance' with the stars and the Bodhisattva Ākāśagarbha
the deva Ratnaprabha/'Treasure light' with the name 'Treasure Intention [or 'response' in your translation 寶意]', the sun and the Bodhisattva Avalokitesvara.
I say dodgy tradition, because the earliest quotes we have of it are by Zhiyi and Jizang in their commentary on the Lotus Sutra and neither of them names the source for their quote (just 'some people say' or 'there is a sutra that says'). That doesn't mean much on its own but later writers in the Tang Dynasty who do give a source mention two different sutras that are both thought to have been composed in China. I'm not sure if either of these apocryphal sutras are still available, but there some lengthy quotations from them in other works, and they are full of Chinese mythology.
Another problem with identifying Ratnaprabha with the sun is that in the Sanskrit version of the Lotus sutra the list of devas is expanded and there is Ratnaprabha deva-putra and Sūrya['Sun'] deva-putra.
Perhaps you could see Jizang and Zhiyi as sceptically reporting a commonly held folk belief among Chinese Buddhist at the time - that the three devas at the start of the Lotus Sutra represent the Moon the Stars and the Sun. On the one hand they can't find solid scriptural basis for it, on the other if they didn't mention it then their commentaries might seem incomplete.
Chinese leads for those who want them:
EDIT: oh, I see how you get 'Treasure Response'. There's a further development in the Tang, when we get rid of the deva Samantagandha who represented the stars, and just have two deva/Boddhisattvas representing the sun and the moon. In this version Ratnaprabha has changed his name again: treasure light 寶光 -> treasure intention 寶意-> treasure response 寶應聲. This is the only stage of development in which a source is named.