By Ben Dummett 

Online retailer Signa Sports United is nearing a deal to raise money from a group of investors including Saudi Arabia's sovereign-wealth fund, according to people familiar with the matter.

Saudi Arabia's Public Investment Fund would join Signa's earlier backers, including Japan's SoftBank Group Corp., and Abu Dhabi sovereign-wealth fund Mubadala Investment Co., the people said. It would mark a reunion of sorts for the three investors, who were the cornerstones of SoftBank's $100 billion Vision Fund, launched in 2016.

The total investment by the group and other investors would total more than $370 million, according to people familiar with the matter, and link to Signa's plan to go public in New York through its previously announced merger with Yucaipa Acquisition Corp., a special-purpose acquisition company, or SPAC, led by California billionaire Ron Burkle. The deal could be announced as soon as Friday.

The investment is a private investment in public equity, or PIPE, a common type of structure that enlarges the amount of money raised as part of SPAC mergers. The money will be earmarked for future investments in the business and acquisitions to fuel growth.

Berlin-based Signa oversees a sports e-commerce and technology platform focused on the sale of bikes and tennis equipment as well as outdoor and team sportswear. The company's online sites operate primarily in Europe and the U.S. and include Fahrrad.de, Bikester, Probikeshop, CAMPZ and Tennis-Point.

Signa's SPAC merger, along with the investment from PIF and others, will value the enlarged company at $3.2 billion. It is expected to be completed by the end of the year. As part of that tie up, Signa is also buying online bike retailer WiggleCRC from European buyout firm Bridgepoint Group PLC.

A SPAC, or blank-check company, raises money and trades on a stock exchange with the sole intent of merging with a private company and taking it public. It can prove a faster way to go public than the traditional initial-public-offering route.

Signa plans to use the fresh cash to boost its presence in the U.S. It wants to take advantage of the move to online purchases accelerated by the pandemic, and the growing adoption of electrical bicycles, according to a company investor presentation.

The deal underscores PIF's focus on sports-related investments. Saudi Arabia's Crown Prince Mohammed bin Salman put sports and entertainment at the center of a national economic and social transformation. Last week, a group led by the sovereign-wealth fund struck a $380 million deal to acquire soccer club Newcastle United of the English Premier League.

Signa has forecast that the U.S. market will generate 9% of its total $1.6 billion net revenue for the fiscal year ended Sept. 30. That assumes completion of the WiggleCRC acquisition and its purchase in May of Tennis Express, a Texas-based tennis online retailer. In the U.S., Signa also operates Midwest Sports, another online tennis retailer based in Ohio.

In the prior fiscal year, Signa's net revenue totaled $849 million all of which was generated from sales in Continental Europe and the U.K.

Write to Ben Dummett at ben.dummett@wsj.com