We know Lord Vishnu's avatars and we mostly have knowledge of different forms of deities and their leela. But does our scriptures have any accounts of avatars of Parabrahma?
Yes, certainly. But NOT in the same sense as of those of say, Lord Vishnu or Lord Shiva. The reason for this is that the nature of the Parambramhm (Parbramha) is fundamentally different from that of both - ordinary souls like us, who are linked to casual ( and ultimately to gross ) bodies, as well as the divine souls residing in the higher realms.
The gross forms which we refer to as incarnations, exist as material personifications of the divine beings ( read Gods ), who in spite of there divinity, are incomplete aspects of the Supreme Brahma, just like us ( except when they are in yoga with the Consciousness , of course ) .
There incarnations are therefore aspects of and by extension casual incarnations of Parbramha.
Being the 'casual actor' responsible for the the apparent existence of the worlds and beings, it is clearly absurd to speak of there being a personification of the Brahma in one gross body more than in any other, with the possible exception of the divine beings and their incarnations.
All the above points have been sufficiently reconfirmed by both sages and scriptures, for there to be any need for a citation.
Clearly, it is impossible to find a scriptural reference to an avatar of the kind you enquired about ( not TOO sure about this ) . However, it is true that these exist and that we are among them.
Do not be confused about Parabrahma and Vishnu. Parabrahma is Vishnu. Parabrahma is Shiva. Parabrahma is everything. Every deity is a representation of Parabrahma.
Brahmanyo devakiputro brahmanyo madhusudanom
Brahman is Devaki's son, Brahman is Madhusudana.
Rudra Hridaya Upanishad:
Thus everybody should prostrate to Sri Maha Vishnu with great devotion. He is the Atman. He is the Paramatman. He is the Antaratman. Brahma is the Antaratman. Shiva is the Paramatman. Vishnu is the Eternal Atman of all this universe. This whole creation of Svarga, Martya and Patala Lokas is a big tree. Vishnu is the top portion (branches) of this tree. Brahma is the stem. The root is Lord Shiva.
The effect is Vishnu. The action is Brahma. The cause is Shiva. For the benefit of the worlds. Rudra has taken these three forms.
Rudra is Dharma. Vishnu is the world. Brahma is Knowledge. Therefore, do Kirtan of His name, 'Rudra', 'Rudra'. By singing like this, the hallowed name of this great Lord, all your sins will be destroyed.