"another portion of" is correct and usable in written English.
It is used to refer to another part or segment of something that has already been mentioned. Example: "I have eaten half of the pizza, but there is another portion of it left for you."
But Palestinians used a bulldozer to knock down another portion of the wall separating Egypt and Gaza.
Another portion of the lamp takes inspiration from the shell-like roofs of the Sydney Opera House.
He apologized that another portion of his reporting archive, skulls dug up from shallow graves, was unavailable for review.
Alessandrojacopo Boncompagni Ludovisi, who lives on another portion of the estate, is also making wine there and calling it Fiorano.
They kept another portion of the money in an envelope that ended up embedded in a vent.
From the outside, Seaport looks like a decent alternative to the homelessness that defines another portion of the city's mentally ill.
In another portion of her interview, Renna described a poster with a list of names that had been removed from Kelly's office wall.
In the letter, he suggested that allowing the companies to buy higher-priced mortgages would extend an "implied guarantee to another portion of the mortgage market".
In 1998 another portion of the war-torn country the SSDF-controlled area in the northeast, identified as Puntland announced its intentions to self-govern.
Given the strong demand, the Swiss financial firm submitted an unsolicited bid to the New York Fed for another portion of A.I.G. assets, prompting the latest auction.
At the same time, however, some of the calcium ions are being removed from the sarcoplasm by another portion of the sarcoplasmic reticulum, the longitudinal tubules.
